The present invention relates to a control device for driving a bipolar switchable power semiconductor component, wherein the control device is designed to apply an electrical voltage to a gate terminal of the power semiconductor component and, in order to turn off the power semiconductor component, to reduce the electrical voltage from a first voltage value to a second voltage value. In addition, the present invention relates to a semiconductor module having such a control device. Finally, the present invention relates to a method for controlling a bipolar switchable power semiconductor component.
In this case the interest is focused on bipolar switchable or deactivatable power semiconductor components. Such a bipolar switchable power semiconductor component can be, in particular, an IGBT. When turning off bipolar switchable power semiconductor components, the charge carriers required for the flow of current must be dispelled. When conventional and reverse-conducting IGBTs are turned off by dispelling the charge carriers, this results in high electrical field strengths. As a result of this field strength loading, the power semiconductor component cannot be shut down at any arbitrary speed. Furthermore, the rate of increase of the electrical voltage on the load terminals is limited primarily by the requirements of the load. Both the charge carrier concentration in the power semiconductor component and the switching speed affect the turn-off losses of the power semiconductor component. To minimize the losses the switching speed—limited by the safe operating range that must be maintained—is set as high as possible. This is normally effected by means of a suitable choice of the magnitude of a gate discharge current.
The gate of the turned-on power semiconductor component is charged to an electrical voltage with a first voltage value. When turning off the power semiconductor component, the gate is discharged via a resistor to an electrical voltage with a second voltage value. The electrical voltage is therefore reduced from the first voltage value to the second voltage value. The transition from the conducting state with a high charge carrier concentration to the de-energized state results in comparatively high turn-off losses.
DE 39 05 645 A1 discloses a control method for improving the overcurrent turn-off behavior of power semiconductor switches with MOS control input. Furthermore, DE 102 06 392 A1 discloses a method and a device for optimizing the turn-off process of a non-latching, deactivatable power semiconductor switch. Finally, DE 10 2015 220 594 A1 discloses a semiconductor drive unit and a power converter which uses the former.
The object of the present invention is to specify a solution as to how a bipolar switchable power semiconductor component of the aforementioned type can be more efficiently turned off.